Pitch prevention by addition of ligand and organic sulfonate



United States Patent 3,398,047 PITCH PREVENTION BY ADDITION OF LIGAND AND ORGANIC SULFONATE Raymond J. Michalski, Riverdale, Ill., assignor to Nalco Chemical Company, Chicago, 11]., a corporation of Delaware No Drawing. Filed Oct. 8, 1964, Ser. No. 402,628 7 Claims. (Cl. 162-48) ABSTRACT OF THE DISCLOSURE This invention deals with treating pulp and paper mill systems to prevent the deposition of pitch in such systems. This is achieved by treating these systems with a composition consisting of a blend of a ligand and an organic sulfonate.

The instant invention is concerned with an improvement in the making of paper. More specific-ally, the present invention relates to a method of preventing deposition of pitch and other precipitants which commonly occur in pulp and paper mill systems.

Recently, the problem of occurrence of deposits of various substances upon equipment employed in pulp and paper mill systems has assumed a position of increasing importance and as well has become more difficult to control. Such deposits generally result in offgrade production, increased maintenance costs, decreased production because of breaks, requirement of more frequent washups, and excessive raw material usage.

One of the most serious problems causing one or more of the above undesirable results in deposition of pitch upon paper and pulp mill equipment, transfer lines, storage tanks, etc. This problem has become more prevalent and burdensome of late due to increased utilization of lower grade pulps from pulp wood of high pitch content. With usage of green pulp woods, pitch deposition becomes increasingly ditficult to handle, resulting in overfrequent shutdowns and loss of production.

The problem of pitch deposits is one which has been found to manifest itself at practically all points in numerous pulp and paper mill operations at one time or another. Quite often it is found that deposits particularly occur at a point in the system shortly after a high degree of de-fibering or after a point of stock dilution. Generally the pitch is released from the pulp in the form of small water-insoluble particles. These particles subsequently agglomerate and deposit upon the fibers and any available surface in the pulp and paper mill system which they contact.

A number of methods of pitch control are employed to combat the just-discussed problem. This includes the use of pitch solvents, polyphosphates, talc, clays, etc. While these have met with some measure of success, in many instances proper pitch control cannot be effected even with benefit of one or more of the above or other additive chemicals employed in the papermaking operation. It would therefore be of benefit to the papermaking art if a composition could be discovered which had excellent activity in controlling pitch deposition. Moreover, if a single composition could be devised which could be usefully employed to inhibit pitch depositions in both pulp and paper mill systems of varying types, such additive would find ready acceptance in the paper field. In view of the above, it therefore becomes an object of the invention to provide an improved papennaking process.

A more specific object of the invention is to provide a method of preventing deposition of pitch and other deposits in pulp and paper mill systems by application of a single extremely effective paper additive composition.

Still another object of the invention is to provide a chemical composition compatible with an aqueous pulp stream which is effective in preventing pitch deposition at economical dosages without fear of deleterious sideeffects.

Other objects will appear hereinafter.

In accordance with the invention, a new and improved method of preventing deposition of pitch and other deposits in pulp and paper mill systems has been discovered. In its broadest aspects, the invention lies in treating a pulp being processed in either of said systems with a pitch control composition in at least an amount sufficient to substantially inhibit the pitch deposition. The pitch control material should include an organic polydentate ligand and an organic sulfonate. By applying these materials in concerted action, surprising efficiency in prevention of pitch deposition is noted.

The organic polydentate ligand material is one which is normally characterized as possessing the ability to form chelate structures. Preferred for use in the invention are multidentate chelating agents which have threeeight donor atoms. These materials are well-known and their structures need little elaboration. Two treatises dealing with a number of organic polydentate ligands are Chemistry of the Coordination Compounds by J. C. Bailar, Jr., Reinhold Publishing Corporation, 1956 and Chelating Agents and Metal Chelates by F. P. Dwyer and D. P. Mellor, Academic Press, 1964.

Preferred polydentate ligands for use in the instant invention include ethylenediamine, glycol, glycerol, mannitol, sorbitol, mono-, di-, and triethanol amines; oxalate and malonate salts; salicylic, lactic, citric, glycollic and tartaric acids; iminodiacetic acid, glycine, nitrilotriacetic acid, ethylenediamine-tetraacetic acid and salts thereof; diketones as acetylacetone, propylenediamine, stilbenediamine, aromatic diamines, biguanide, substituted quinolines, phthalocyanines, porphins, triglycine, etc.

Greatly preferred ligands are aminopolycarboxylic acids and sugar acids. Among the aminopolycarboxylic acids the following are illustrative: ethylenediaminediacetic acid, ethylenediaminedipropionic acid, ethylenediaminetetraacetic acid, 1,2 propylenediaminetetraacetic acid, 1,2 cyclohexanediaminetetraacetic acid, -N- hydroxyethylethylenediaminetriacetic acid.

Salts of the above listed acids or other polyaminocarboxylic acids work equally well in the invention. Alkali metal and alkaline earth metal salts are most preferred to {form carboxytlate materials. Partial salts, that is, amino acids only partly neutralized to varying degrees, may likewise be employed without loss of activity in prevention of pitch deposition. Among the just-named materials the trisodium salt of N-hydroxyethylethylene diaminetriacetic acid is most preferred.

Another class of greatly preferred polydentate ligands is a sugar compound, and more particularly a sugar acid or salt of a sugar acid. These sugar acids are carbohydrates having carboxylic acid function to a greater or lesser degree. Preferred sugar acids or salts are those in which there is at least one carboxylic group or carboxylic salt group per molecule. Generally, these sugar acids or salts have three or more carbon atoms in the molecule. Representative types are sodium heptogluconate, sodium salt of glycoxyacetic acid, various wood sugars and their salts removed from a cook liquor obtained in pulping of wood such as soft woods, carboxylic acids or acid salts of glucose, allose, dextrose, sucrose, etc. Mono-, di-, tri-, and tetra saccharides having some free carboxyl character or carboxylic salt function may all be usefully employed. Preferred substances are sodium heptogluconate, and the so dium salt of glucoxyacetic acid.

If the sugar acid is derived from reaction of a sugar, such as sucrose, and a halocarboxylic acid or acid salt such as chloroacetic acid or sodium chloroacetiate, it is preferred that a molar ratio of acid or acid salt to sugar of from 1:1 to 4.1 be employed.

The following example illustrates preparation of a typical sugar acid useful in the invention to inhibit pitch deposition.

EXAMPLE I 15.20 parts of sucrose, 4.50 parts of chloroacetic acid and 3.80 parts of 50% sodium hydroxide were added together and allowed to react at about room temperature while mixing was effected. The strong base was present to neutralize any hydrochloric acid formed in the reaction between the chloroacetic acid and sucrose. The resultant product can be used directly as one of the components of the compositions of the invention.

The other component used in making up the pitch control compositions of the invention is an organic sulfonate. Again, these materials are well-known products of commerce. Both alkyl and aryl sulfonates as well as alkaryl sulfonate substances may be employed. For example, petroleum sulfonates are a useful class. Particularly preferred organic sulfonates are water-soluble lignosulfonates, substituted aryl sulfonates and naphthalene sulfonates.

Particularly preferred are water-soluble lignosulfonates derived as by-products in the manufacture of sulfite pulp where wood is cooked with calcium bisulfite-magnesium bisulfite-sulfur dioxide liquor. In this process the lignin is converted to lignosulfonic acid which is thereafter converted to a solid salt product such as calcium lignosulfonate, ammonium lignosulfonate, potassium lignosulfate, sodium lignosulfonate, etc.

Preferred naphthalene sulfonates are those materials which contain one or more sulfonated naphthalene nuclei. Examples of water-soluble naphthalene sulfonates which can be used in accordance with the invention are polymethylene-bis-naphthalene sulfonate, the sodium or potassium salts thereof, and alkyl naphthalene sulfonates or the sodium or potassium salts thereof in which the alkyl group contains about 1-12 carbon atoms. Other preferred sulfonates are substituted aryl sulfonates such as sodium xylene sulfonate.

When used in combination to control the deposition of pitch, the organic polydentate ligand and organic sulfonate are preferably present as set out in Composition I below:

Composition I Component: Percent by weight Ligand -80 Sulfonate -90 A more preferred composition of the invention includes the respective components in the following proportion:

Composition II Component: Percent by Weight Ligand 10-60 Sulfonate 40-90 In a specific embodiment of the invention, it is preferred that a non-ionic wetting agent be employed along with the above described components. Preferred classes of non-ionic materials are the alkyl substituted ethoxylated phenols and polyalkoxylated aliphatic substances. Other suitable non-ionics wetting agents are the wellknown Pluronic materials which are block copolymers of propylene and ethylene oxide and are described in U.S. Patent 2,674,619. For a more comprehensive and detailed list of various non-ionic wetting agents that may be used, reference may be made to the publication, Detergents and Emulsifiers to Date by John W. McCutcheon, John W. McCutcheon, Inc., 1963.

The pitch control compositions of the invention may be applied in solid admixture with or without non-ionic wetting agent or in form of an aqueous solution. In some instances a combination of water and polar organic solvents may be used as the solvating medium. Materials such as alcohols, acetone, dimethyl formamide, sulfoxides, etc. may be employed, as Well as host of other polar organics. Preferred organic solvating materials are methanol, ethanol, and isopropyl alcohol.

Again, the respective components which make up the composition of the invention may be added to the pulp or paper mill system separately or in combination. It is greatly preferred that the chemical pitch control agents be added in the form of a single composition, and more preferably in solvent media.

Illustrative solutions of pitch control reagents are given as follows:

Composition III Component: Percent by weight Sodium lignosulphonate 30.0 Sugar acid (primarily sodium salt of glucoheptonic acid-34-38% solids) 30.0 Isopropyl alcohol 9.0 Water 31.0

Composition IV Sodium xylene sulfonate 25.0 Isopropyl alcohol 15.0 Water 30.0 Polyalkoxylated aliphatic base 20.0 Trisodium salt of N-hydroxyethylethylenediaminetriacetic acid 10.0

The pitch control compositions of the invention may be added to either a pulp or paper mill and are particularly necessary at any point where physical mastication of fiber takes place. At these points release of pitch substances is more prevalent.

Thus the additive combination may be added in the pulp mill at points such as at the grinders, blow-pits, washers, chests, showers, blending and/or storage tanks etc.

In the paper mill the pitch control compositions may be incorporated into the pulp stream at the heaters and refiners. Likewise, the composition of the invention may be added to the headboxes, repulpers following washers, lines, etc. Occurrence of pitch is particularly noticed on the Fourdrinier wire and wet press felts. Thus, application of the pitch control composition at any point in the stream prior to formation of the wet web itself assists in preventin formation of pitch at the just mentioned areas.

Again, the pitch control agents of the invention may be employed in any type of pulp and paper mill system designed to produce a wide variety of paper products. Generally, 0.01-20 lbs. of pitch control chemical comprising ligand and sulfonate per ton of pulp (dry weight) gives effective control. More preferably 0.05-10 lbs. per ton are employed. The materials are particularly desirable for control of pitch in groundwood and sulfite mills. However, it is understood that the invention is not limited to the particular type of pulp and paper mill under treatment.

In order to illustrate the efiicacy of the invention, the following examples are given by way of illustration. It is understood, of course, that the invention is not limited thereto.

EXAMPLE II In this test a paper mill located in the northwest area of the country was treated with Composition IV whose chemical make-up was outlined above. The mill was engaged in making napkin on a Fourdrinier machine operating at pH 7-8. Total hardness of the water was 195 ppm. The tray water temperature was -90 F. The stock furnish was primarily bleached sulfite with some bleached kraft. Previously, a pitch control program employing 2.5 pounds of prior art pitch control material per ton of pulp added to the beater had been unsuccessful. Particularly, pitch control problems occurred by way of deposit build-up on the table rolls, wire return rolls, and wire itself. Also, pitch deposition occurred on the press roll doctor blades and in the head box. Composition IV at a level of 0.25-.5 pound per ton added to the beater gave excellent results and substantially inhibited pitch deposition in all areas.

EXAMPLE III At a southern unbleached kraft mill, Composition IV was fed continuously to .the secondary fan pump at a level of 0.25 pound per ton. The secondary head box was maintained completely free of deposits. Heretofore, no pitch control chemical tested had been effectual.

' EXAMPLE IV Composition IV was here tested in a midwestern tissue mill using groundwood, blended sulfite and waste paper furnish. Before application a pitch problem occurred in the machine area on the wires and the felts. Composition IV was fed at a level of 1 pound per ton to the heaters with excellent results. The wires were run about 30 days before any cleaning whatsoever was necessary when the proper pitch control program was carried out employing Composition IV.

It was also noted that the composition of the invention while particularly effective in preventing pitch deposition also control deposition of other materials of varying type whether they occur in form of lumps, stringers, beards, ropes, etc. More particularly, the pitch control agents of the invention are useful in preventing deposits of a number of types, including microbiological slimes, fibrous materials and hydrated fines, chemical substances such as alumina, silica, clay, starch, titanium dioxide, and barium salts, calcareous deposits, resinous materials, iron, etc.

The invention is hereby claimed as follows:

1. A method of preventing the deposition of pitch and other deposits in pulp and paper mill systems of the til type wherein pulp is masticated and then formed into a sheet which comprises the step of feeding to such systems at a point prior to sheet formation from 0.01 to 20 lbs. of a pitch control composition per ton of pulp on a dry weight basis, said pitch control composition consisting of the following components:

(A) from 10-80% by weight of a ligand from the group consisting of: polyaminocarboxylic acids, sugar acids, and salts thereof; and

(B) from 2090% by weight of an organic sulfonate from the group consisting of: lignosulfonates, substituted aryl sulfonates and naphthalene sulfonates.

2. The method of claim 1 wherein component (A) is present in an amount ranging from 10 by weight and component (B) is present in an amont ranging from 40-90% by weight.

3. The method of claim 1 wherein said lignosulfonate is an alkali metal lignosulfonate.

4. The method of claim 1 wherein said sugar acid is sodium heptogluconate.

5. The method of claim 1 wherein said ligand is the trisodium salt of N-hydroxyethylethylenediaminetriacetic acid.

6. The method of claim 1 wherein said pitch-control composition additionally contains a non-ionic wetting agent.

7. The method of claim 6 wherein said non-ionic wetting agent is a polyalkoxylated aliphatic compound.

References Cited UNITED STATES PATENTS 2,753,309 7/1956 Figdor 162190X 3,071,504 1/1963 Dunklin 162-199 3,256,140 6/1966 Poschmann 162190 OTHER REFERENCES Brauns: The Elimination of Pitch Trouble, Pulp and Paper of Canada, pp. 333-336, September 1932.

DONALL H. SYLVESTER, Primary Examiner. 

